A major limitation preventing the effective treatment of bacterial infections is an inability to image them in vivo with accuracy and sensitivity. Consequently, bacterial infections can be diagnosed only after they have become systemic or have caused significant anatomical tissue damage, a stage at which they are challenging to treat owing to the high bacterial burden. Although contrast agents have been developed to image bacteria, their clinical impact has been minimal because they are unable to detect small numbers of bacteria in vivo, and cannot distinguish infections from other pathologies such as cancer and inflammation. There is therefore a great need for the development of contrast agents that can image small numbers of bacteria accurately in vivo.
Bacteria can utilize glycogen, starch, and amylose as carbon sources. Prior to transport through the cell membrane, these polysaccharides are hydrolyzed by the extracellular α-amylase into smaller maltodextrins, maltose and isomaltose. Maltose ABC importer (type I) of Escherichia coli enables the bacteria to feed on maltose and maltodextrins. Bordignon et al., Mol Microbiol., 2010, 77(6):1354-66.
Positron emission tomography (PET) is nuclear medicine imaging technique that produces a two- or three-dimensional image in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide (tracer), which is introduced into the body on a biologically active molecule. 2-Deoxy-2-(18F)fluoro-D-glucose, an analogue of glucose, is a commonly used human tracer for PET imaging. The concentrations of tracer imaged then give tissue metabolic activity in terms of regional glucose uptake.
Beta-cyclodextrin has been contemplated for affinity based delivery of an antibiotic through non-covalent interactions. See Thatiparti & Recum, Macromol. Biosci., 2010, 10, 82-90.